The invention is in the field of devices aiding the handicapped, and particularly wheelchair passengers, to board and deboard vehicles, including commercial vehicles and private vans. Several styles of these devices are in use, and those developed by the inventor of the device disclosed herein are of the type wherein a fold-out step panel arrangement is used in which the step horizontal surfaces and risers are hinged together. When used as a step, the panels are folded into a step configuration, but can subsequently be used as a platform by extending the panels out horizontally on a carriage sttructure that also, once extended, can be hydraulically driven upwards or downwards to raise or lower a passenger in a wheelchair on the platform between the vehicle surface and the sidewalk or boarding platform.
Patents issued to the inventor and co-workers on this type of alternate step/platform lift mechanism include U.S. Pat. Nos. 4,081,091 issued 03/28/78; 4,027,807 issued 06/07/77; and 4,176,999 issued 12/04/79. Additionally, a pending application, Ser. No. 06/268,466 is a continuation-in-part of a Patent Cooperation Treaty Application which was in turn a coninuation-in-part of U.S. application Ser. No. 06/041,943, now U.S. Pat. No. 4,251,179.
These lifts work quite well and have been very sucessful in the marketplace. Their primary application lies in transit buses, private vans, and the transit company mini-buses that are used in some cities as an accommodation to the handicapped in place of equipping all of their buses with the wheelchair lift.
These lifts have been constructed to define two steps intermediate the vehicular floor and the passenger platform or sidewalk, which is ideal for buses and vans. However, in some trolleys and other rail vehciles, the distance between the vehicle floor and passenger platform is sufficiently great that another step is required, so that three steps are ideal.
Because the forerunner two-step lift structure has been engineered virtually to perfection, ideally, rather than re-engineering that basic concept to incorporate yet a third step, a better solution would lie in the provision of an auxiliary step to use in conjunction with the two-step lift.